The proposed research will address unresolved issues regarding the airflow involved in human voice production, focusing on the formation and evolution of jet flows in the glottal and pharyngeal regions. The glottal jet is hypothesized to play a key role in the flow-induced vibration of the vocal folds and in the production of voiced sound, as well as a central role in determining both voice efficiency (through turbulent dissipation) and voice quality (through producing perturbations and fluctuations in voiced sound output). This hypothesis rests on the well-established instability of jet flows, which may lead to variations in the formation and evolution of the jet across vocal fold vibration cycles. A central consideration to the proposed work is, then, to what extent glottal aerodynamics may be considered quasisteady. The degree to which the glottal jet manifests these effects has not yet been directly addressed, in part because what experimental data exists concerning glottal jet behavior was obtained using invasive point measurement techniques. These methods preclude systematic study of cycle-to-cycle variations in both the spatial and temporal structure of the jet. In addition, previous modeling of glottal flow has considered the effect of the jet in a limited manner. The proposed research will address these issues directly, making use of recent advances in computational and experimental fluid dynamics techniques, which have not yet been applied to speech science. In vitro experiments in which the instantaneous particle velocity and acceleration fields of a water flow through a moving vocal fold wall model are successively measured in real time using video Particle Image Velocimetry/Accelerometry (PIV/A). In order to assure spatial and temporal resolution, the glottal model is scaled up and the appropriate Reynolds number and Strouhal number ranges (500<Re<4000, 0.01 <St<0. 1), are preserved. Vortex-element methods will be used to provide rapid computation of jet formation, evolution, and sound production. The computational results, validated by the proposed experiments, will also be compared to predictions made by previous glottal flow models. The proposed research brings to bear a unique combination of expertise in the diverse fields of articulatory speech synthesis, flow-induced vibration, turbulent flow, and flow-induced sound.